Speedstep – Intel’s mobile CPU dynamic power management architecture

Just a few weeks after its launch of the Dixon, Intel demonstrated a revolutionary new mobile processor technology that was expected to close the performance gap between mobile PCs and their historically higher performance desktop counterparts. The demonstration was of a dual-mode mobile processor technology – codenamed Geyserville – that allowed a mobile PC user to operate at a higher frequency when plugged into a wall outlet and automatically switch to a lower power and frequency when running on battery, conserving battery life. The technology was subsequently introduced aboard mobile 600MHz and 650MHz Pentium III processors in early 2000 – under the name SpeedStep.

SpeedStep technology offers mobile users two performance modes: Maximum Performance mode and Battery Optimised mode. The system by default automatically chooses which mode to run in, depending on whether the computer is running on batteries or mains power. When running in Battery Optimised Mode, the processors ran at 500MHz and 1.35V, significantly lowering CPU power consumption and consequently preserving battery life. When a user plugged into an AC outlet, the notebook automatically switched to Maximum Performance Mode, increasing the voltage to 1.6V and the speed to the maximum the processor was capable of.

These transitions happen in only 1/2000 th of a second – so fast they are completely transparent to users, even if they occur in the middle of performance-intensive applications such as playing a DVD movie. Users also have the freedom to select the Maximum Performance Mode even while running on batteries. Making that switch is as easy as clicking an icon at the bottom of the screen, with no reboot required.

Intel has developed both the hardware and software components to make the SpeedStep technology work seamlessly, including the system BIOS, end user interface software, switch control ASIC and support in the chipset. No change to operating systems or software applications is needed in order to take advantage of the technology.